The present invention relates to a pressure sensor that detects deflection of a thin portion of a substrate, to detect a pressure of fluid, and a method of manufacturing the same.
Heretofore, there has been known a pressure sensor as disclosed in Japanese Unexamined Patent Publication No. 11-118642, as a pressure sensor that detects deflection of a thin portion of a substrate, to detect a pressure of fluid.
Such a pressure sensor consists of a substrate, a blocking plate and a piezoresistive element.
A pressure receiving recess is formed on a rear face of the substrate, to thereby form a thin portion on a surface side of the substrate.
A frame shaped protruding portion is formed on a surface side of the thin portion of the substrate by means of an etching process of an insulating film, and the blocking plate is laid on the protruding portion, to thereby form a standard pressure chamber.
Further, the piezoresistive element that detects deflection of the thin portion is disposed on the surface side of the thin potion that is surrounded by the frame shaped protruding portion.
Then, the deflection of the thin portion caused according to a difference between a pressure of fluid introduced into the pressure receiving recess, and a pressure in the standard pressure chamber, is detected by the piezoresistive element.
However, in the pressure sensor described above, when the frame shaped protruding portion is formed on the substrate, sometimes particles of the insulating film or resist are adhered to a part surrounded by the protruding portion.
Since the protruding portion is formed by means of the etching process of the insulating film as described above, it can protrude only by about 1 xcexcm from the surface of the substrate.
Contrary to the above, there may be the case where particles of the insulating film or resist are higher than the height of the protruding portion.
Therefore, the particles of the insulating film or resist are trapped between the blocking plate and the thin portion of the substrate, to prevent the deflection of the thin portion. Thus, pressure detection accuracy is lowered.
Here, if it is investigated whether or not the particles of the insulating film or resist are adhered to the part surrounded by the protruding portion and, in the case where the particles are adhered, an operation for removing the particles is performed, it is possible to prevent the lowering of detection accuracy. However, there is caused a problem in that working manpower is increased, resulting in an increase of manufacturing cost.
Therefore, an object of the present invention is to provide a pressure sensor capable of detecting a pressure with high accuracy, even in the case where particles of an insulating film or resist are adhered to a part surrounded by a frame shaped protruding portion.
In order to achieve the above object, the present invention is constituted so that a recess for increasing the height of space surrounded by the frame shaped protruding portion is formed on at least one of a surface of a thin portion surrounded by the frame shaped protruding portion and a rear face of a blocking plate.
Other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.